The present invention relates to a stirring device for use in inspection of samples in chemical and biochemical fields, which is designed to mix reagents, reaction liquids or the like and to stir the resultant mixture.
Stirrers, each having piezoelectric elements, are superior to rotary-type stirrers in terms of stirring efficiency. They therefore help to enhance the operating performance of automatic analyzers.
A conventional stirrer having piezoelectric elements will be described, with reference to FIGS. 2A, 2B and 2C. FIG. 2A is a front view, FIG. 2B is a rear view, and FIG. 2C is a side view.
This stirrer has a so-called "bimorph" structure. That is, it comprises a metal shim 201 and two piezoelectric ceramic elements 202 are attached to both surfaces of the shim 201. The metal shim 201 and the elements 202 constitute an actuator.
When an AC voltage is applied to the piezoelectric ceramic elements 202, the elements 202 are repeatedly expand and contract. The metal shim 201 is thereby vibrated. One end of the shim 201 is held in place by a screw 203. The other end of the shim 201 extends with the same material having a narrow portion, thus forming a blade 204. The blade 204 is inserted into a reaction cell and immersed in the liquid contained in the reaction cell. By the metal shim 201 is vibrated, the blade 204 is vibrated, so the liquid in the reaction cell is stirred. The weight of the screw 205 controls the vibration amplitude of the blade 204.
A cover 206 conceals all but the blade 204. Cover 206 protect the vibration of the piezoelectric ceramic element.
In recent years it has been demanded that automatic analyzers be made smaller and that two or more automatic analyzers be used in combination. To make an automatic analyzer, the reaction tubes in the reaction tank of the analyzer are arranged at a shorter distance.
An automatic analyzer may have two stirrers that are arranged side by side when they stir the liquid in two adjacent reaction tubes at the same time. To stir the liquid in the two adjacent reaction tubes, the stirrers need to be spaced for the same distance as the reaction tubes are spaced apart. If the stirrers are arranged very close to each other, their covers 206 may interfere with each other.
Therefore, reducing the distance between adjacent blades 204 has its limit, so the distance between the adjacent reaction cells is limited. Consequently, the automatic analyzer cannot be made as small as is demanded.